Pressure induced valence transitions in<b><i>f</i></b>-electron systems

Temmerman, W. M.; Svane, A.; Petit, L.; Lüders, M.; Strange, Paul; Szotek, Z.

doi:10.1080/01411590701228703

Cited by 11 publications

(7 citation statements)

References 83 publications

(101 reference statements)

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“…We have studied the 5f valence configurations of U in UPt 3 and UPd 3 [13,14] 3 has an enhanced linear specific heat coefficient γ, characteristic of heavy fermion materials, and has been shown to become superconducting at low temperatures [15]. The large specific heat coefficient is correlated with a large density of states (DOS) at the Fermi level, which is in agreement with the U 5+ configuration predicted from our calculations.…”

Section: Intermetallicssupporting

confidence: 68%

Self-interaction corrected local spin density calculations of actinides

Petit

Svane

Szotek

et al. 2010

IOP Conf. Ser.: Mater. Sci. Eng.

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Rare-earth pnictides and chalcogenides from first-principles L Petit, Z Szotek, M Lüders et al. Abstract.We use the self-interaction corrected local spin-density approximation in order to describe localization-delocalization phenomena in the strongly correlated actinide materials. Based on total energy considerations, the methodology enables us to predict the ground-state valency configuration of the actinide ions in these compounds from first principles. Here we review a number of applications, ranging from electronic structure calculations of actinide metals, nitrides and carbides to the behaviour under pressure of intermetallics, and O vacancies in PuO 2 .

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Section: Intermetallicssupporting

confidence: 68%

Self-interaction corrected local spin density calculations of actinides

Petit

Svane

Szotek

et al. 2010

IOP Conf. Ser.: Mater. Sci. Eng.

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“…Ultimately the degree of f -band filling becomes such that the gain in energy associated with localizing the given f -state becomes more important than the corresponding loss in band formation energy, and the divalent scenario becomes the ground state (scenarios (C') and (F')). 30 As seen in Fig. 5, owing to the additional electron, in the chalcogenides the filling of f -states sets in much earlier than in the pnictides, which explains why the trivalent scenario is relatively more dominant in the pnictides.…”

Section: Electronic Structure a Density Of States: Chalcogen Versus P...mentioning

confidence: 88%

Rare earth monopnictides and monochalcogenides from first principles: towards an electronic phase diagram of strongly correlated materials

et al. 2010

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We present results of an ab-initio study of the electronic structure of 140 rare earth compounds. Specifically we predict an electronic phase diagram of the entire range of rare earth monopnictides and monochalcogenides, composed of metallic, semiconducting and heavy fermion-like regions, and exhibiting valency transitions brought about by a complex interplay between ligand chemistry and lanthanide contraction. The calculations exploit the combined effect of a first-principles methodology, which can adequately describe the dual character of electrons, itinerant vs. localized, and high throughput computing made possible by the increasing available computational power. Our findings, including the predicted "intermediate valent" compounds SmO and TmSe, are in overall excellent agreement with the available experimental data. The accuracy of the approach, proven e.g. through the lattice parameters calculated to within ∼1.5% of the experimental values, and its ability to describe localization phenomena in solids, makes it a competitive atomistic simulation approach in the search for and design of new materials with specific physical properties and possible technological applications. PACS numbers:

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“…Valence fluctuations play an essential role in some of the f -electron systems most exciting behaviors, such as quantum criticality and unconventional superconductivity [1,2]. But their understanding has proven challenging to capture in a unified theory because they arise from subtle many-body interactions between the f electrons and the conduction states [3,4]. Pressure on the other hand is an efficient way to act on f -electron interactions and localization and thus can serve as a window onto the f -electron physics.…”

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confidence: 99%

Unified understanding of the valence transition in the rare-earth monochalcogenides under pressure

et al. 2013

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Valence instability is a key ingredient of the unusual properties of f electron materials, yet a clear understanding is lacking as it involves a complex interplay between f electrons and conduction states. Here we propose a unified picture of pressure-induced valence transition in Sm and Yb monochalcogenides, considered as model system for mixed valent 4f -electron materials. Using high-resolution x-ray absorption spectroscopy, we show that the valence transition is driven by the promotion of a 4f electron specifically into the lowest unoccupied (LU) 5d t2g band. We demonstrate with a promotional model that the nature of the transition at low pressures is intimately related to the density of states of the LU band, while at high pressures it is governed by the hybridization strength. These results set a new standard for the generic understanding of valence fluctuations in f -electron materials. PACS numbers: 71.20.Eh, 78.70.Ck, 75.20.Hr Valence fluctuations play an essential role in some of the f -electron systems most exciting behaviors, such as quantum criticality and unconventional superconductivity [1,2]. But their understanding has proven challenging to capture in a unified theory because they arise from subtle many-body interactions between the f electrons and the conduction states [3,4]. Pressure on the other hand is an efficient way to act on f -electron interactions and localization and thus can serve as a window onto the f -electron physics. Notably, the pressure-induced valence transition of the lanthanide monochalcogenides is a paradigmatic illustration of f delocalization phenomena and their tremendous diversity. For instance, SmS undergoes a first-order transition to near-trivalency coinciding with the onset of magnetic ordering [5], whereas the transition of YbS into an intermediate-valent correlated metal is extremely sluggish [6]. These diverse behaviors, while establishing a severe test bed for theoretical understanding of f -electron systems, have been overlooked for the past decades. Here, we address them in the light of a direct measurement of the electronic structure of Sm and Yb monochalcogenides (SmS, SmSe, SmTe, YbS, YbSe) under pressure performed using highresolution x-ray absorption spectroscopy in the partial fluorescence yield (PFY-XAS) mode. Our data reveal that the valence discontinuity and concomitant closing of the gap under pressure are caused by the specific filling of the lowest unoccupied (LU) 5d t 2g band by a 4f electron, offering a unified picture of electron delocalization and intermediate valency. Using a promotional model, we show that both the steepness and the amplitude of the valence transition of the Sm compounds increase with the density of states (DOS) of this LU band. When exceeding a critical DOS, the transition becomes first order for SmS. The model fails to describe the prolonged transition of the Yb compounds, which suggests that at high pressures the valence transition is impeded by enhanced hybridization. Ultimately, we suggest that our analysis can serve ...

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Pressure induced valence transitions inf-electron systems

Cited by 11 publications

References 83 publications

Self-interaction corrected local spin density calculations of actinides

Self-interaction corrected local spin density calculations of actinides

Rare earth monopnictides and monochalcogenides from first principles: towards an electronic phase diagram of strongly correlated materials

Unified understanding of the valence transition in the rare-earth monochalcogenides under pressure

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